A new generalized method for dna-assisted assembly can mix and match two different types of nanoparticles to create new multifunctional materials (Image: BNL)

Researchers at the Brookhaven National Laboratory (BNL) have developed a generalized method of blending two different types of nanoparticles into a single large-scale composite material using synthetic DNA strands. The technique has great potential for designing a vast range of new nanomaterials with precise electrical, mechanical or magnetic properties.

The "mix and match" approach

Assembly of nanostructures using synthetic DNA isn't new, and has already been used to combine two or even three different types of nanoparticles into a single material. However, the process as it stands comes with a number of limitations, such as the inability to control the distance between the nanoparticles.

The technique developed at BNL is much more generalized and can be used to control parameters such as the spacing and ordering of the different particles, allowing for the mixing and matching of nanoparticles with different magnetic, optical, or chemical properties.

Physicist Oleg Gang and his team first coat the two kinds of nanoparticles with binding chemicals and then attach them to two complementary strands of lab-synthesized DNA. When the two DNA strands are placed in close proximity, they help the nanoparticles mix and match into a very large three-dimensional array.

The approach circumvents problems that scientists previously had to face, such as the magnetic forces that usually prevent nanoparticles of different kinds or shapes from mixing together in an organized, highly regular structure with predictable properties.

Gang and colleagues are able to influence crucial aspects of the final material by changing certain process parameters. For instance, changing the thickness of the nanoparticle coatings can increase the regularity in the final three-dimensional atomic structure, and the length of the DNA strands used can change the distance between particles from 10 to 100 nanometers.

Applications

It's hard to say exactly what kind of impact this development could have, but its potential is certainly great, as is the number of possible materials that could be created using the technique.

In demonstrating their method, the researchers produced a composite of gold and magnetic nanoparticles whose phase and ordering of particles can be changed simply by applying an external magnetic field, which could suggest a new way to create better magnetic switches or materials that can change shape on demand.

Another area of interest as far as applications go are quantum dots, nanocrystals so small in size that they display quantum properties. This advance could lead to quantum dots mixed with magnetic particles so that their fluorescence can be controlled by an external magnetic field or, for example, dots whose brightness is enhanced by gold nanoparticles.